Once all your donuts have been shaped, preheat a cast iron skillet over medium heat and combine cinnamon and sugar coating on a plate.
Set the cinnamon sugar plate and a clean plate next to your cast iron skillet. You'll want this nearby!
Add a liberal amount of coconut oil to your skillet. I call for about 6 tbs, but you want it to be about 1 inch deep.
Once the oil is completely preheated, place your donuts into the oil and watch them sizzle!
After about a minute, drop the heat to low and let them cook on that side until a crust has formed on the bottom. This should take about 3 minutes.
Flip your donuts and let cook on the other side until a crust has formed. This should take about 3-5 minutes.
Once the other side has cooked, do a quick flip again to add oil to the other side and place the dounuts in the cinnamon sugar. Flip the donuts around to coat all sides. Then transfer coated donuts to a clean plate.
Do this process for your next batch.
If your donuts are still gooey on the inside just place them in a 350 degree F oven for 5-10 minutes after coating with cinnamon sugar and they will be completely baked on the inside but crunchy on the outside.